Six seats, five weeks — that’s the number of pick-ups the Democrats need in order to gain control the Senate, plus the amount of time in which they have to do it.

At a minimum, Democrats must beat Republican incumbents in five close contests (Missouri, Montana, Ohio, Pennsylvania, and Rhode Island), score a surprise win somewhere else (Arizona, Tennessee, or Virginia), and fend off an increasingly strong GOP challenge in New Jersey.

Since my previous update, I’ve changed Virginia from “likely Republican” to “leaning Republican.”

Herewith, a roundup of the 20 most interesting races.

ARIZONA: Although Democratic businessman Jim Pederson has improved his standing over the last several months, so has Republican senator Jon Kyl. A new Arizona State University poll of likely voters gives Kyl the lead, 49 percent to 38 percent. He benefits from the fact that there are more Democrats supporting him (19 percent) than there are Republicans supporting Pederson (10 percent) — a case study in the advantages of incumbency. LIKELY REPUBLICAN RETENTION

CONNECTICUT: The new “comeback kid” is Sen. Joe Lieberman, who lost the Democrat nomination in August but is now poised for re-election as an independent. A poll of likely voters released last week by Quinnipiac University shows him beating Democratic nominee Ned Lamont, 49 percent to 39 percent, with GOP candidate Alan Schlesinger at only 5 percent. Although Lamont leads among Democrats, 57 percent to 37 percent, Lieberman is propped up by strong support among Republicans (69 percent) and independents (50 percent). Lieberman has said that if he’s reelected, he’ll once again caucus with Democrats — so this race won’t affect the balance of the Senate, but it may have much to say about the future of the Democratic party. LIKELY DEMOCRATIC RETENTION

FLORIDA: Could it be any worse for Republicans in Florida? Why yes, it could: Imagine if disgraced former congressman Mark Foley were the Senate nominee — earlier this year, he had considered entering the race, to save the GOP from the embarrassing defeat it will now face with congresswoman Katherine Harris. Democratic senator Bill Nelson will trounce Harris — a new Research 2000 poll of likely voters puts him ahead, 55 percent to 37 percent — but that’s nothing compared to the embarrassment he would have delivered upon Foley. LIKELY DEMOCRATIC RETENTION MARYLAND: Republican Lt. Gov. Michael Steele is an impressive candidate, but he faces an uphill battle against Democratic congressman Ben Cardin. Steele is counting on black voters who are disenchanted with a Democratic slate of candidates that doesn’t exactly look like Maryland to split their tickets. Last week, a Baltimore Sun survey of likely voters put Cardin ahead, 50 percent to 41 percent. LEANING DEMOCRATIC RETENTION

MICHIGAN: A newly released poll of registered voters, conducted for Inside Michigan Politics, gives Democratic senator Debbie Stabenow a commanding lead over Republican nominee Michael Bouchard, 52 percent to 30 percent. Other surveys have suggested that the race is closer, and Michigan Republicans have a history of underperforming in polls as compared to the actual turnout. Still, this looks like too much ground for Bouchard to make up, even in a state that’s in a grumpy mood due to job losses. LEANING DEMOCRATIC RETENTION MINNESOTA: Democratic county attorney Amy Klobuchar continues to have a much easier time of this race than Republicans had hoped: In last week’s St. Paul Pioneer Press survey of likely voters, she held a large lead over Republican congressman Mark Kennedy, 52 percent to 37 percent. Will the GOP’s decision to hold its 2008 convention in Minneapolis help Kennedy make up a point or two? LEANING DEMOCRATIC RETENTION

MISSOURI: This is an exceedingly close contest between Republican senator Jim Talent and Democratic state auditor Claire McCaskill. The most recent poll, by SurveyUSA and of likely voters, gave McCaskill 48 percent and Talent 47 percent. TOSS UP

MONTANA: No senator has a higher disapproval rating than the GOP’s Conrad Burns, now locked in the race of his life against Democratic state Senate president Jon Tester. A Mason-Dixon poll of likely voters, released yesterday, puts Tester at 47 percent and Burns at 40 percent. Republicans hope that voters will come to realize that Tester is far more liberal than he is currently perceived to be; the Democrat’s recent call to repeal the Patriot Act may help. TOSS UP

NEBRASKA: Democratic senator Ben Nelson can take a vacation in October and he’ll still beat Republican businessman Pete Ricketts. LIKELY DEMOCRATIC RETENTION NEVADA: Jimmy Carter failed to carry Nevada in both 1976 and 1980; his son, Democratic nominee Jack Carter, will extend the family’s losing streak next month, when Republican senator John Ensign beats him soundly. A Las Vegas Review-Journal poll of likely voters put Ensign well ahead, 58 percent to 35 percent. LIKELY REPUBLICAN RETENTION NEW JERSEY: Republicans smell an opportunity here, thanks to a brewing ethics scandal involving Democratic senator Bob Menendez. There’s some concern that Democrats may “pull a Torricelli” and replace Menendez with a different nominee, as happened in 2002. But the Torricelli-for-Lautenberg switcheroo was made almost exactly four years ago today, so time is running short. A Rutgers University poll released last week gave Menendez a slight lead among likely voters (45 percent to 44 percent) and Kean a small edge among registered voters (42 percent to 40 percent). This race probably will remain close to the end, but it also has the potential to break decisively for the GOP in the next week or so. TOSS UP

NEW YORK: Democratic senator Hillary Rodham Clinton will comfortably defeat the GOP nominee, former Yonkers mayor John Spencer. Last week, a CBS News/New York Times poll of registered voters put the race at 58 percent for Clinton and 29 percent for Spencer. LIKELY DEMOCRATIC RETENTION

OHIO: Democratic congressman Sherrod Brown continues to hold a slim lead over Republican senator Mike DeWine, 45 percent to 43 percent, according to Mason-Dixon’s poll of likely voters, released yesterday. It’s hard to bet against the incumbent, but this is a tough year for the GOP in Ohio. Would DeWine be doing better if Republican governor Bob Taft, who is enormously unpopular after an ethically challenged and lackluster tenure, had resigned? TOSS UP

PENNSYLVANIA: Republican senator Rick Santorum has said that his race is to Democrats what the South Dakota race featuring Democratic senator Tom Daschle two years ago was to Republicans — a contest that party activists around the country are desperate to win. It’s a good analogy, and right now Democratic state treasurer Bob Casey Jr. remains ahead: A GOP poll of likely voters released last week put the contest at 50 percent for Casey, 41 percent for Santorum, and 5 percent for Green candidate Carl Romanelli. The fact that Santorum’s numbers have improved only slightly since the start of the year — and potentially have worsened since August — spells trouble for the incumbent. But all along, his campaign has insisted that October would be the crucial period and that the only poll that counts is the one of actual voters on Election Day. TOSS UP

RHODE ISLAND: Senator Lincoln Chafee, a RINO (i.e., “Republican In Name Only”), beat off a strong primary challenger from Steven Laffey last month. Now he faces Democratic former attorney general Sheldon Whitehouse in what will probably become the most expensive race in state history. A Republican poll of likely voters, conducted right after the primary, gave Whitehouse an edge, 45 percent to 40 percent — but 21 percent of independents were undecided and those who had committed themselves leaned toward Chafee. Conservatives are still wondering why the national GOP has made Chafee’s re-election a high priority when so many other races are competitive. TOSS UP TENNESSEE: Last week, Democrats were delighted to see a new poll of likely voters that shows Democratic congressman Harold Ford Jr. moving ahead of Republican Bob Corker, 45 percent to 39 percent. GOP operatives were careful to point out that it was conducted by a Democratic consulting group. A Maxon-Dixon poll of likely voters, released yesterday, had Ford at 43 percent and Corker at 42 percent. The bottom line is that this race has become closer than Republicans wanted or expected. LEANING REPUBLICAN RETENTION

VERMONT: Socialist congressman Bernie Sanders — an “independent” who votes with Democrats — is running well ahead of Republican businessman Richard Tarrant, 58 percent to 33 percent, according to a Research 2000 poll of likely voters. LIKELY DEMOCRATIC RETENTION

VIRGINIA: The last six weeks have been the worst of Republican senator George Allen’s political career. They’ve taken a toll: His race against Democratic nominee James Webb is much closer than anticipated. Over the weekend, a Mason-Dixon survey of likely voters had the contest tied at 43 percent and a SurveyUSA poll put it at 50 percent for Allen and 43 percent for Webb. If Allen campaigns well in October — no guarantee, of course — he should pull off a narrow victory. LEANING REPUBLICAN RETENTION WASHINGTON: Over the summer, several surveys suggested that GOP businessman Mike McGavick was trailing Democratic senator Maria Cantwell by only four or five points. A GOP poll of likely voters, released last week, indicates that Cantwell has widened her margin: She leads, 49 percent to 40 percent. There is some grumbling that McGavick, who has pledged to run a positive campaign, might benefit from a few negative ads that persuade voters to ditch their incumbent. LEANING DEMOCRATIC RETENTION WEST VIRGINIA: The ancient Democratic senator Robert Byrd should defeat GOP challenger John Raese. But will the mainstream media ever start cracking Strom Thurmond-style jokes about his age? LIKELY DEMOCRATIC RETENTION

— John J. Miller is national political reporter for National Review and the author, most recently, of A Gift of Freedom: How the John M. Olin Foundation Changed America.